1. Field of the Invention
The present invention relates, generally, to communication systems and processes which use radio frequency (RF) transmitters and receivers (transceivers), and, in particular embodiments, to systems and processes for multi-mode, multi-band Code Division Multiple Access (CDMA) and Global System for Mobile (GSM) communication transceivers that share functional blocks to minimize size, weight, complexity, power consumption, and cost.
2. Description of Related Art
It has become increasingly important to minimize the size, weight, complexity, power consumption, and cost of various electronic devices, especially personal communication devices such as cellular telephones, personal pagers, cordless telephones, and the like. One way to minimize such characteristics is to minimize the number of components and functions required in the electronic device, or to perform multiple functions using the same components. However, personal communication devices such as cellular telephones often require complex circuitry with a number of power-inefficient components for performing particular functions. This is especially true in modern cellular communications, where several different communication standards are employed worldwide, and cellular telephones with the flexibility to operate under multiple communications standards are highly desirable from a consumer and manufacturing perspective.
For example, the GSM communication standard is a world-wide mode of digital cellular communication operating over three different frequency bands. GSM-900 operates in the 900 MHz frequency band and is currently used in Europe and Asia. DCS is another digital cellular standard based on GSM technology, operating in the 1800 MHz frequency band and also currently used in Europe and Asia. The United States uses PCS, a third digital cellular standard similar to DCS, but operating in the 1900 MHz band. GSM is currently used in approximately 154 countries, including the geographic areas of North Africa, India, China, Europe, the Middle East, and Taiwan.
However, GSM is not the only mode of cellular communication. CDMA is another mode of digital cellular communication operating in either the 900 or 1900 MHz band. CDMA is one of the most widely used modes of cellular communication in the United States, and is the most widely used mode of cellular communication in Korea. CDMA is also being used in China, India, and Taiwan.
With improved voice and data communications and political climates continuing to expand the world market, a xe2x80x9cworld telephonexe2x80x9d capable of operating in many different countries would be of interest to international business travelers. Multi-mode, multi-band cellular telephones with shared functionality and an optimized architecture capable of operating under all of these standards afford consumers widespread applicability and allow manufacturers to benefit from the cost-efficiency of a common design.
However, multi-mode, multi-band cellular telephones such as combined CDMA/GSM telephones present a number of design challenges. Conventional single-band transmitters typically require two separate frequencies, a fixed intermediate frequency (IF) for modulation and a tunable RF for upconversion. Conventional single-band receivers also typically require two separate frequencies, a tunable RF for downconversion and a fixed IF for demodulation. Thus, a single-band cellular telephone may require as many as four different frequency sources. CDMA/GSM multi-band and multi-mode cellular telephones exacerbate the problem because the modulation, upconversion, downconversion, and demodulation processes for each band and mode may operate at different frequencies and amplitudes. Furthermore, the frequencies and amplitudes employed by each band and mode may require different filters and amplifiers for the transmit and receive function of each band. The design challenge of producing cellular telephones of minimal size, weight, complexity, power consumption, and cost is thus compounded by multi-mode, multi-band cellular telephones.
Therefore, it is an object of embodiments of the present invention to provide a system and process for a multi-mode, multi-band CDMA and GSM communication transceiver that shares functional blocks to minimize size, weight, complexity, power consumption, and cost.
These and other objects are accomplished according to a communication system for communicating CDMA and GSM transmit and receive RF information signals through one or more antennas. The communication system is comprised of a transmitting unit, a receiving unit, and at least one antenna. The transmitting unit modulates and upconverts a transmit baseband information signal to generate a CDMA transmit RF information signal and a GSM transmit RF information signal. The receiving unit downconverts and demodulates a CDMA receive RF information signal and a GSM receive RF information signal to generate a receive baseband information signal. One or more antennas are coupled to the transmitting unit and receiving unit for transmitting the CDMA transmit RF information signal and the GSM transmit RF information signal, and receiving the CDMA receive RF information signal and the GSM receive RF information signal.
The transmitting unit comprises a modulator for modulating a transmit IF local oscillator frequency (LO) with the transmit baseband information signal to generate a transmit IF information signal. It also includes a plurality of upconverters for upconverting the transmit IF information signal with a GSM transmit RF LO to generate the GSM transmit RF information signal, and for upconverting the transmit IF information signal with a CDMA transmit RF LO to generate the CDMA transmit RF information signal.
The receiving unit comprises a downconverter for downconverting the CDMA receive RF information signal with a receive RF LO to generate a receive IF information signal, and for downconverting the GSM receive RF information signal with the receive RF LO to generate a receive IF information signal. It also includes a demodulator for demodulating the receive IF information signal with a receive IF LO to generate the receive baseband information signal.
A transmit IF variable gain amplifier is coupled between the modulator and the plurality of upconverters for amplifying the transmit IF information signal. The plurality of upconverters includes a translation loop for upconverting the transmit IF information signal with the GSM transmit RF LO, and an upconverter mixer for upconverting the transmit IF information signal with the CDMA transmit RF LO.
These and other objects, features, and advantages of embodiments of the to invention will be apparent to those skilled in the art from the following detailed description of embodiments of the invention, when read with the drawings and appended claims.